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8.2 List of faults
9. Disposal
This product or parts of it must be disposed
of in an environmentally sound way.
Use appropriate waste collection services.
If this is not possible, contact the nearest Grundfos
company or service workshop.
Subject to alterations.
Fault
Possible cause
Possible remedy
Dosing flow too high
Inlet pressure greater than
backpressure
Install additional spring-loaded valve
(approx. 3 bar) on the discharge side.
Increase pressure differential.
No dosing flow or
dosing flow too low
Air in dosing head
Deaerate the pump.
Faulty diaphragm
Change the diaphragm
(see section
7.3 Perform service
).
Leakage/fracture in lines
Check and repair lines.
Valves leaking or blocked
Check and clean valves.
Valves installed incorrectly
Check that the arrow on the valve housing is
pointing in the direction of flow. Check whether all
O-rings are installed correctly.
Blocked suction line
Clean suction line/install filter.
Suction lift too high
Reduce suction lift.
Install priming aid.
Viscosity too high
Use hose with larger diameter.
Install spring-loaded valve on the discharge side.
Deaeration valve open
Close the deaeration valve.
Irregular dosing
Valves leaking or blocked
Tighten up valves, replace valves if necessary
(see section
7.3 Perform service
).
Backpressure fluctuations
Keep backpressure constant.
Liquid escaping from
the drain opening on
the flange
Faulty diaphragm
Change the diaphragm
(see section
7.3 Perform service
).
Liquid escaping
Dosing head screws not
tightened
Tighten up screws
(see section
4.2 Hydraulic connection
).
Valves not tightened
Tighten up valves/union nuts
(see section
4.2 Hydraulic connection
).
Pump not sucking in
Suction lift too high
Reduce suction lift; if necessary, provide positive
inlet pressure.
Backpressure too high
Open the deaeration valve.
Soiled valves
Flush system, replace valves if necessary
(see section
7.3 Perform service
).
